Retrograde peristalsis is a muscular movement of hollow organs such as the esophagus, stomach, intestines, ureters, uterus, and fallopian tubes. In this movement, they actively transport their contents against the physiological direction. Retrograde peristalsis has a protective function and occurs physiologically in the intestine to store stool.
What is retrograde peristalsis?
Retrograde peristalsis is a muscular movement of hollow organs such as the intestines. Medicine uses retrograde peristalsis to describe a specific transport movement of the esophagus, stomach, colon, or ureter, as well as the uterus or fallopian tube in women. These structures are called hollow organs in anatomy because they do not form a continuous compact mass of cells and instead comprise an interior space. This cavity is also known as the lumen; a skin-like covering tissue (epithelium) covers the inside of the cavity, while smooth muscle is found in the outer layers. During peristalsis, these muscles contract, thereby forcing the contents of the hollow organ to move in a specific direction. Nerves of the autonomic nervous system control the smooth muscles, which humans cannot control voluntarily. Medicine also calls transport in the normal direction orthograde peristalsis. Retrograde peristalsis, on the other hand, describes transport in the opposite direction and is therefore also called antiperistalsis.
Function and task
Smooth muscle surrounds hollow organs. Its name is reminiscent of the flat surface of the musculature: It lacks the transverse muscle striations characteristic of striated muscle. Compared to it, smooth muscle uses less energy and oxygen, but works more slowly. The parasympathetic nervous system controls retrograde peristalsis. The parasympathetic nervous system is a part of the autonomic nervous system. It controls involuntary processes that cannot be voluntarily initiated or interrupted by the individual. These processes are highly automated and thus require very little brain capacity. Activation of the sympathetic nervous system, the activating part of the nervous system, usually inhibits peristalsis. However, the parasympathetic nervous system is not solely responsible for retrograde peristalsis: especially in the stomach and ureter, intrinsic reflexes of the organs also trigger the transport movement. During peristalsis, the smooth muscles of a hollow organ contract in a ring shape, thereby constricting the lumen. The constriction forces the contents to move in a specific direction-in retrograde peristalsis, opposite to the physiological direction. The contraction continues in the direction of transport, thereby pushing the contents of the hollow organ bit by bit in the desired direction. Retrograde peristalsis of the esophagus and stomach is used primarily during vomiting. The esophagus actively transports the food pulp so that it does not close. It also allows smaller remnants to be removed from the esophagus. In this way, the esophagus protects itself from irritation and serious damage caused by stomach acid. Remaining esophageal debris also poses a potential risk of infection. In the small and large intestines, peristalsis moves the intestinal contents in a physiological direction toward the rectum. However, the movements of the colon are not continuous; they occur in phases. The digestive system of a healthy person goes through one to three such periods of movement per day. Their number depends on various factors, for example, the physical activity of the person or the fiber content of the food. Retrograde peristalsis allows the colon to temporarily store stool. It is triggered not only by the parasympathetic nervous system, but also by the local peristaltic reflex of the intestine. In women, peristalsis serves to transport the egg in the fallopian tube. Furthermore, the peristalsis of the uterus supports the breakdown and removal of the mucous membrane during menstruation. It also plays an important role in the birth process.
Diseases and ailments
Normally, peristalsis of the colon results in up to three bowel movements per day, depending on physical activity, dietary fiber content, consumption of bowel-stimulating substances, and other factors. In addition, psychogenic influences also play a role in the frequency of peristalsis.Medicine speaks of constipation when the bowel empties less than once in three days. Common symptoms of constipation include pain in the lower abdomen, an unnatural feeling of fullness, pressure- and movement-related pain, flatulence, and the impression of incomplete emptying during bowel movements. Prolonged constipation poses a risk for several reasons: The stool can physiologically obstruct the bowel and, in extreme cases, completely block the bowel; the bowel walls can suffer mechanical damage and even rupture due to hardened stool. In such a case, there is a risk of excrement entering the abdominal cavity, where numerous organs are located. Penetrating bacteria and debris can then cause infections that can affect the tissue between the organs as well as the organs themselves. The retrograde peristalsis of the colon can prevent this to some degree. The retrograde peristalsis of the stomach also performs a protective function. If a person consumes potentially toxic substances, the body may initiate a series of reflexes and involuntary reactions. The organism can induce vomiting via the gag reflex and antiperistalsis. In this process, the muscles of the stomach contract and reduce the volume of the stomach to such an extent that its contents push out. The contraction of the esophageal muscles also assists in the transport of the possible toxins out of the body. The active transport movement is even more important than orthograde peristalsis because it must transport the food pulp against both the normal direction and gravity.